In a food processor, pulse the onion with the cilantro until finely chopped. Add the tomatoes and pulse until finely chopped. Add the olive oil, red wine vinegar, pimentón and cayenne and pulse just until blended. Transfer the salsa to a bowl and season with salt.

Make Ahead
The salsa can be refrigerated for up to 2 days.
NotesPimentón or Spanish paprika, is available in many styles, from sweet to smoky. The pimentón from La Vera, in the Cáceres region, is ground from dried red peppers smoked over oak. It is available at Latin markets.
Serve WithGrilled Skirt Steak with Hot Chilean Salsa .